Michael Feinstein (left) and Dame Edna star together in "All About Me."

One of the gimmicks behind the new Broadway show “All About Me” is that its two stars — Dame Edna Everage and Michael Feinstein — have such, shall we say, “healthy egos” that there’s bound to be an onstage collision.

But from what I’m hearing, there’s been some colliding offstage, as well.

Feinstein is miffed that he’s being relegated to the sidelines by Edna’s shenanigans, which are threatening to run away with the show.

“Michael’s not laughing at the jokes Edna’s making about him,” a source says. “He’s upset that everything she does upstages him.”

Well, what, for God’s sake, did he expect?

As W.C. Fields famously said, “Never work with children or animals or Dame Edna.”

At a press stunt for the show the other day — “The Search for Dame Edna’s Understudy” (check it out at nypost.com) — I asked Feinstein about the situation.

The cabaret fixture gamely replied: “Well, one of things we’ve put in the show is the real-life contretemps between Edna and me. I think the show is balanced. I have my solo moments, and she has hers. We’ve had to create an uneasy truce.”

Edna was unavailable for comment, but I did ask her manager, Barry Humphries, who’s so close to Edna that he almost is Edna, about his egomaniacal client.

“Frankly, she’s been impossible,” he acknowledged. “And Michael’s had to put up with a lot. But he does occupy part of the stage. It’s a very, very small part of the stage, but it’s all his.”

In addition to the tension between the stars, “All About Me” has another problem: Nobody, including the people working on it, seems to know quite what it is yet — even though it begins previews Monday.

“It changes every day,” one source says.

Another adds: “It changes every minute.”

The show was always kind of a slapdash affair. When the original director, Jerry Zaks, left in December to work on the ailing “Addams Family,” the producers turned the show over to a new director, Casey Nicholaw, without any fuss.

“One day Jerry’s the director, the next day Casey is,” marvels a veteran producer. “Can there be much of a show if you can change directors so easily?”

Christopher Durang is credited as the book writer, but up until just a few days

ago the second act wasn’t much more than an outline.

Durang’s contributions are a mystery to some, since a lot of the material comes from Edna’s enjoyable old bag of tricks.

A high-level production source, who requested anonymity because of the sensitive nature of the subject, said of Durang: “He scribbles, darling. Some people might call it writing. I call it scribbling.”

The source added: “I have to be careful what I say to you, but when this is all over — and it might be by next week! — I’ll spill the beans.”

Congratulations, by the way, to Scott Mason, who was named Dame Edna’s “honorary understudy.”

Humphries announced that Mason would be “compensated” for his effort. “Not financially,” Humphries added quickly, “but you will be given seats to the show with a very limited view of the stage.”

The great Betty Buckley has returned to Feinstein’s at the Regency this month with a terrific new show, “For the Love of Broadway!”